The Chief Operator of the wastewater treatment plant for a local industrial facility had reported one of his Hoffman air blowers was beginning to vibrate more than usual. I was called in to inspect the installation and collect vibration & temperature data from his 75 HP motor/blower units. Two of the units were operating just fine, but the 3rd blower did indeed have lightly elevated overall vibration levels. It was also running a little hotter than normal.
Although the vibration levels were not high enough to be considered alarm level, I did find the bearing condition reading indicated probable bearing wear. This acceleration reading I measure is an "envelope spectrum" of the high frequencies where elevated levels indicate lack of bearing lubrication, or bearing wear. After removing the bearing housing cover to inspect the condition of the grease lubrication, I found there was plenty of grease, and in relatively good condition. The opposite drive end bearing was apparently defective.
There were also relatively high axial plane vibration levels. Normally, axial plane vibration levels should be less than half of those in the radial plane. The amplitudes in the axial plane on this motor/blower unit were higher than the vertical plane levels, which indicates possible shaft misalignment, and/or coupling looseness or wear. Further inspection of the installation revealed the Woods' flexible coupling was very worn and damaged.
Since the bearings in this blower were at least 10 years old, we opted to replace both blower bearings, as well as install a new coupling flex element and laser align the shafts. Vibration levels in all 3 planes decreased by at least half, to well within acceptable levels at .08 in/sec velocity. Both bearing condition levels now measured like new at .05 g's/sec acceleration.
This operator was "in tune" with the operation of his equipment. If he hadn't noticed the slight change in operation and called me in to complete an analysis of the equipment operation, the inevitable bearing failure could have been catastrophic. A complete blower rebuild would cost a lot more than this bearing replacement. Having a good, effective preventative maintenance program in place is a good concept, but having well trained, dedicated personnel will keep the equipment running.
Proper training will keep equipment running healthier and longer, thus reducing costly repairs and downtime. Invest in PM and operator training, it will save you money!
